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Advanced Energy Sources and Controls for Metal Additive Manufacturing

Description:

 
 

TECHNOLOGY AREA(S): Materials/Processes

ACQUISITION PROGRAM: EPE-FY-17-03 FNC entitled "Quality Metal Additive Manufacturing" or QUALITY MADE

OBJECTIVE: To develop a new energy source or improve an existing energy source or integrate multiple energy sources with their control units into a metal Additive Manufacturing system to better characterize and control key aspects of the metal AM process prior to, during and after processing of each layer.

DESCRIPTION: At the heart of any additive manufacturing (AM) process is the energy source that powers the thermodynamic forces that drive the metallurgical transformations that produce the microstructure that define the quality of the manufactured metallic parts. In order to make certifiable AM parts (i.e. defect and residual stress free parts with controlled microstructure and narrow tolerances) it is critical to control all aspects of the energy delivery system.

There are multiple parameters that control the microstructure of AM parts. Each particular AM process will have its own list of key control parameters. Some of these parameters include (without grouping them by process): the powder size distribution; powder layer thickness; wire feed velocity; energy beam spot size; melt pool temperature profile; the cooling rate; melt flow dynamic characteristics; evaporation rates and many others. As the process volume becomes smaller (to better control dimensional tolerances and microstructure) and as the process energy scanning speeds become faster (due to the faster heating and cooling rates associated with the smaller volumes) the requirements for higher precision, adaptability and agility of the energy source become more stringent. Most of the existing energy sources have some of these characteristics, but in order to further improve the quality of metal AM parts new or improved energy sources are required that have more of them.

Also, the AM process has inherent pre-, in-, and post-process variabilities associated with the powder size distribution, small processing volumes, high processing energies and fast scanning speeds that can affect the layer quality (such as surface roughness, microstructure distribution, residual stresses, alloy composition changes, defects). Accounting and correcting these variabilities is critical if we are to build quality metal AM parts. Since feedback control of the energy processing source is nearly impossible at the typical processing speeds found in most AM systems, it is highly desirable that as much information as possible is gathered of each layer before AM consolidation as well as after AM consolidation for purposes of feedforward control. Energy sources that can be used to characterize the AM material before processing and the consolidated layer after processing for purposes of feedforward control are desirable.

Finally, some of the desired attributes of the energy source and control unit could be, but are not limited to: dynamic control of the power level; energy excitation frequency; pulse duration and repetition rate, spot size control and energy distribution. Another desirable attribute of the energy source and control unit is the ability to switch to a low energy mode enabling in-situ measurement of various build parameters before, during and/or after the processing of each AM layer for building quality AM parts. Parameters such as: the powder layer quality and thickness prior to melting; monitoring certain aspects of the melting process (power level, melt pool temperature); and parameters after the melt processing could include measurement of the quality of the finished layer (surface profile, defect distribution) are critical for building quality AM parts via feedforward control.

For purposes of parameter estimation to assist with proposal preparation, the objective of this program is to develop an agile, adaptable and precise energy source and controller capable of AM'ing a quality part that weighs approximately 1 kg and occupies a volume of no more than 1 cubic foot in approximately 1 day.

PHASE I: During Phase I (concept formulation and development) the small business will determine, for the specific energy source that it chooses for this program, the key system parameters that need to be controlled and the ranges required to process common AM metallic feedstock material (such as Ti-6Al-4V, 316L SS, Inconel 625, Ni) to make quality AM parts. The small business will define and develop a protocol to characterize the AM material prior to processing, during processing and/or after processing each layer for purposes of feedforward control. This protocol should not add more than another day to the build process for a total of 2 days. During the Phase I the small business will validate key aspects of the concepts that were formulated to demonstrate feasibility.

Once all the key system parameters are determined and during the Phase I Option if awarded, the contractor will perform a preliminary design of the energy delivery and control system for making quality AM parts. Depending on the time and resources available during Phase I Option the contractor will start buying, testing and assembling the parts to build the system (energy source and controller). For the purpose of this program, a quality AM part is defined as one that is defect and residual stress free with controlled microstructure and narrow dimensional tolerances.

PHASE II: The Phase II effort should result in prototype development and validation of the system. The contractor will perform a detailed design of the system and will complete the purchase of all components and assemble the unit following the design established during Phase I. The contractor will write all the firmware and software code necessary to drive all the components of the system to produce the highest level of precision, adaptability and agility of the energy source in order to fabricate “quality AM parts”. The contractor will select a material system from the list provided above for the purpose of making simple geometrical test coupons to support the code development and system optimization tasks. For purposes of system performance validation, the contractor will fabricate a complicated metal AM part and will characterize its “quality”. It is highly recommended that the contractor work with a leading university professor in the field of metal AM and/or with an OEM that could help guide many of these tasks and ultimately provide an integration and transition path.

PHASE III DUAL USE APPLICATIONS: The "Advanced Energy Sources and Controls for Metal Additive Manufacturing" will be transitioned using funding provided by the Navy system program office interested in integrating the SBIR product into a complete AM system. The OEM involved during Phase II will be part of the transition team. Phase III will require integration of the Advanced Energy Sources and Controls with other AM process and controls (such as feedstock delivery system, build volume temperature control, gas handling system) required for a complete Metal Additive Manufacturing system. Private Sector Commercial Potential: Commercial applications include almost all commerce sectors such as: aerospace, shipping, transportation, rail, automobile, medical. Applications include almost all technology areas such as: engine parts, structural parts, mechanical or electrical parts, medical prosthetics, tooth implants. Finally material applications focus is on metals.

REFERENCES:

  • W.E. Frazier, “Metal Additive Manufacturing: A Review”, DOI: 10.1007/s11665-014-0958-z, ASM International, JMEPEG (2014) 23:1917–1928.
  • E. Herderick, "Additive Manufacturing of Metals: A Review", ASM International, Materials Science and Technology, MS&T (2011), 1413-1425.
  • A. Allison, "2014 Additive Manufacturing: Strategic Research Agenda", AM SRA Final Document, TWI (2014), 1-64.

KEYWORDS: Metal Additive Manufacturing, Energy Source, Material Processing, Microstructure, Defects, Residual Stress,

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